The genetic and molecular basis of chemotaxis in Escherichia coli are being studied to provide insight into the processes of sensory transduction and stimulus-response behavior. The chemotaxis machinery in E. coli has been dissected genetically into at least three functional parts: chemoreceptors that detect changes in concentration of attractants and repellants, flagella, the motor organelles of E. coli, and an "integrator" which receives and processes sensory information to produce the appropriate swimming response. The proposed work involves isolation and genetic characterization of mutants defective in various steps of the chemotactic response. The gene products identified through the use of such mutants will then be located chemically by standard labeling and fractionation procedures. Finally attempts will be made to develop functional assays for chemotaxis components by restoration experiments.